1. The first prop is a straw: when Liu sucks, the color rises in the straw; The color fades as soon as it stops. When Liu finally stopped smoking, he could clearly see the color drop. If it is a real liquid, there should be residual coffee in the cup, but there is only something that looks like ice in the cup.

2. The second prop is a cup and coaster: there is a white column in the middle of the cup base, which is a hollow tube with a switch inside. A coaster is like a small quilt, which is filled with a strong hygroscopic substance. The straw also has the function of starting the switch: Liu Yi sucks the straw, the switch is turned on, and the coffee flows downwards; Liu stopped sucking straws, turned off the switch, and the coffee stopped flowing downwards.